The combined effect of climate change and Urban Heat Island (UHI) effect is leading to a rise in air temperature in urban areas, including those with heritage value. Urban morphology and its effect on sun shading conditions in tropical cities is crucial to reduce UHI and improve outdoor thermal comfort. This paper presents a temporal-spatial analysis of the effect of courtyards geometry on their outdoor thermal conditions in a warm-humid climate. The assessment is based on numerical simulations of the mean radiant temperature, by using the RayMan model. Large courtyards geometry (convent typology), in the historical centre of Camagüey, were modelled and analysed changing their height-to-width ratio and orientation. Our findings confirm the effect of varying courtyard tridimensional aspect ratios on outdoor thermal conditions. Aspect ratios higher than 1 are advisable, as they contribute to improve the courtyard thermal conditions in summer, by reducing the subzones in the courtyard where the Tmrt is above 45 °C. Orienting the courtyard's long axis away from the East-West results in a lower level of Tmrt, with reductions of up to 15.7 °C, for high aspect ratios. The obtained Tmrt patterns give information about the most suitable subzones within the courtyards, according to the time of day and season. The proposed design and usability recommendations could be included in renovation projects aimed at enhancing courtyards' thermal conditions and contributing to an improvement of the surrounding urban microclimate.